Bulb · Colchicaceae
Autumn Crocus
Colchicum autumnale
It throws up bare lilac-pink blooms in fall, but every part hides deadly colchicine.
Full sun
Every 7–14 days
USDA 4–9
6–10 in · 15–25 cm
Overview
Autumn crocus catches everyone off guard. Its lilac-pink, goblet-shaped flowers rise straight from bare ground in late summer and fall, with no leaves in sight, which earns it the name naked ladies. The broad strappy foliage shows up the following spring, feeds the corm, and dies back by summer before the next round of bloom.
Despite the name, it is no relation to the spring crocus you might know. It belongs to the family Colchicaceae and grows from a corm rather than a true bulb, naturalizing happily at a woodland edge or scattered through a lawn in zones 4 to 9. Plant it once and it spreads itself into wider clumps year after year.
The catch is serious. Every part of this plant holds colchicine, one of the deadliest compounds in any garden, and there is no antidote if it's eaten. It is beautiful and easy to grow, but it earns a hard line between the flower bed and anything that might take a bite.
Care
The short version: plant the corms in full sun to light shade in well-drained soil, give medium water only while the spring leaves are up, and let those leaves yellow on their own before you tidy them away.
Light
Give autumn crocus full sun for the strongest flowering, though it takes partial shade without much complaint. A woodland edge suits it well, since it gets open light in spring when the leaves are working and dappled shade later in the year.
Water
Provide medium moisture while the foliage is up in spring, then back off almost entirely as the corms go dormant for summer. Sharp drainage is non-negotiable, because soggy ground rots the corm faster than anything else.
Soil
It grows in loam, clay, or sand as long as the soil is organically rich and well drained. A pH from 6.0 to 7.5 covers it, and the one thing that matters most is that water never sits around the corm.
Temperature
This is a cold-hardy plant, comfortable across zones 4 to 9 and tolerant from about -4°F to 75°F (-20°C to 24°C). It needs winter chill to perform and shrugs off hard frost without protection.
Humidity
Ordinary outdoor humidity is all it asks for, so there's nothing to measure or manage. Far more important is keeping the spring leaves dry and uncrowded, since damp, packed foliage invites smut.
Feeding
Work a balanced bulb fertilizer or compost into the soil at planting in fall and that's largely it. The corm stores its own energy from the spring leaves, so heavy feeding does little for it.
Pruning
There's no real pruning to do. Let the spring foliage die back on its own so the corm can stock up for the next bloom, and clear the leaves only once they have yellowed. Never cut the leaves while they're still green.
Repotting
In the ground it wants dividing rather than repotting, every 3 years or so when clumps crowd up. The signs to watch are fewer or smaller flowers, packed clumps, and corms shouldering their way to the surface.
Size & spacing
Plants stay low, reaching about 6 to 10 inches (15 to 25 cm) tall with a similar spread. Set the corms 6 inches (15 cm) apart and 3 to 6 inches deep so each has room to clump up over the years.
When to plant
Autumn crocus runs on its own odd clock. Plant the dormant corms in late summer, around August, and the flowers follow within weeks that same fall. The leaves hold off until the following spring, feed the corm, and fade by midsummer ahead of the next bloom.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not recommended; seed is slow and usually sown outdoors
- Plant: Plant dormant corms 3-6 inches deep and about 6 inches apart in mid- to late summer (August)
- Harvest: Leafless flower stems bloom August to September (late summer to early fall); broad leaves appear the following spring and die back by summer
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Autumn crocus is tough and asks for little, so most trouble comes down to wet soil, hungry slugs, or the floppy habit of its bare stems. Match what you see below and act early. Sharp drainage heads off the one problem that actually kills the plant.
Soft, rotting corms that never sprout
Corm rot sets in when the soil stays wet and waterlogged. Lift a corm and you'll find mushy, discolored, foul-smelling tissue instead of firm flesh. Throw out anything that has rotted and replant the healthy corms in sharply drained ground or a raised bed, because dry feet are the whole defense here.
Fix:
- Discard rotted corms
- Replant healthy corms in sharply drained soil or a raised bed
Chewed corms and ragged holes in new shoots
This is slug and snail damage, and it shows up most in damp, shaded ground. Look for slime trails and soft, gouged patches on corms near the surface, then hand-pick the culprits at dusk or set out bait. Better drainage and less mulch sitting against the corms takes away the cover they hide in.
Fix:
- Hand-pick slugs and snails at dusk
- Set bait or traps around plantings
- Improve drainage and reduce mulch contact on corms
Dark blisters and sooty streaks on the spring leaves
These swollen blisters that burst into dark, powdery spores are fungal smut on the foliage. Pull and destroy any infected leaves as soon as you spot them. The disease takes hold where leaves stay damp and crowded, so space the corms out and keep water off the foliage.
Fix:
- Remove and destroy infected leaves
- Avoid overhead watering and crowding to improve air flow
Bare flower stems leaning and flopping over
This is just the plant's nature, not a problem you can cure. The blooms rise on naked, leafless stems in fall, with no foliage to hold them up, so they lean and topple in wind or rain. Plant them through a low groundcover or among short perennials and the surrounding growth braces the flowers upright.
Fix:
- Underplant with a low groundcover to support stems
- Site among low perennials that hold flowers upright
Toxicity
Treat this plant as a poison, not a snack. Every part holds colchicine, and the corms and seeds carry the most, enough that eating even a little can be fatal to pets, livestock, and people, often with no warning signs for hours. There is no antidote, so the only real safety is keeping it out of reach and washing your hands after you handle it.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
A cat that bites any part of this plant is in real danger. Heavy drooling and bloody vomiting come first, then diarrhea, shock, and damage to the liver and kidneys, with the bone marrow hit later. Signs can lag for hours, so get to a vet on suspicion alone rather than waiting for symptoms.
Dogs Severe
Dogs dig up and chew corms, which are the most concentrated part of all. Watch for drooling, bloody vomiting and diarrhea, collapse, and organ failure that may not appear until well after the meal. This poisoning is often fatal, so treat any nibble as an emergency.
Horses Severe
A grazing horse that takes in autumn crocus suffers violent colic and bloody diarrhea, followed by shock and failing organs. The colchicine works the same way at horse scale, and the outcome is frequently deadly. Call the vet the moment you suspect a mouthful.
Rabbits Severe
There is no safe nibble for a rabbit here. The colchicine in the leaves, flowers, and corms brings on severe gut damage and rapid decline, and small bodies have little margin. Keep this plant entirely out of any space a rabbit can reach.
Livestock Severe
Cattle, sheep, and goats are poisoned by autumn crocus in pasture and in hay, where the toxin stays active even after the plant is dried. Bloody scouring, weakness, and organ failure follow, and animals can die. The bitter taste deters some grazers, but hungry stock and contaminated hay are the real risk.
Birds Severe
Colchicine is poisonous to birds as it is to mammals, and a pecking hen or curious parrot can take a fatal dose from corm or seed. Expect crop and gut distress, weakness, and a fast slide downhill. Keep birds away from the plant and its dropped seed.
People Caution
No part of autumn crocus is food, and people have died mistaking the corms for wild garlic or the plant for true saffron. Eating any part can cause severe vomiting, bloody diarrhea, multi-organ failure, and bone-marrow suppression, with no antidote. Even handling it can irritate the skin, so wear gloves and keep it well away from children.
Keep corms, seeds, leaves, and flowers out of reach of pets and children. Store corms securely, wear gloves when handling as the plant can cause contact dermatitis, and wash hands afterward. Never confuse with culinary saffron.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
The wild species is by far the most common form, but one named selection turns up in gardens.
Pleniflorum
It carries double, rose-pink flowers instead of the single, star-shaped lilac-pink blooms of the species.
Companions
Autumn crocus pairs best with plants that prop up its bare flower stems and share its taste for sun in spring and lighter shade later.
Plant near
Low groundcovers: Help support the weak leafless flower stems and keep blooms from flopping
Deciduous shrubs and woodland-edge perennials: Provide a naturalizing setting with full sun in spring when foliage is present and light shade later
How to propagate
Autumn crocus multiplies easily once it settles in, and the fastest routes all work with the corm rather than waiting on seed.
Offsets & pupsEasy
Lift in summer after leaves die back · Blooms the following fall once established
Each corm spins off smaller offsets around its base. Lift the clump in summer once the leaves have died back, snap the offsets free, and replant them 3 to 6 inches deep and about 6 inches apart. They settle in fast and flower the next fall.
DivisionEasy
Summer after foliage dies back but before flowers emerge; divide every 3 years when crowded · Establishes and blooms the same fall or the next
When a clump crowds itself and flowers fewer, dig and split it. Do this in summer after the foliage dies back but before the flower stems push up, roughly every three years. Divided corms often bloom that same fall, or the one after.
Bulbs & cormsEasy
Plant dormant corms in mid- to late summer (August) · Flowers the same fall after late-summer planting
Set dormant corms out in mid- to late summer, around August, and they flower that very fall. Plant them the moment you get them, because these corms do not keep well in storage and lose vigor fast.
SeedModerate
Sow outdoors when ripe · Slow; seed-grown plants take several years to reach flowering size
Seed is the slow road. Sow it outdoors as soon as it ripens, then wait, because seed-grown plants need several years to reach flowering size. Dividing corms or lifting offsets gets you blooms far sooner.
Myths
Autumn crocus is just a fall-blooming spring crocus and is equally harmless.
These are two unrelated plants. Autumn crocus is Colchicum autumnale in the family Colchicaceae, while true spring crocus belongs to the genus Crocus in the family Iridaceae. Colchicum is loaded with colchicine in every part and is far more dangerous, and you can tell them apart because it carries six stamens to true crocus's three.
Autumn crocus can be used like saffron in cooking.
Never put any part of this plant near food. Eating Colchicum autumnale can kill you because of its colchicine, and the saffron you cook with comes from the wholly unrelated Crocus sativus. The two only share a loose resemblance, nothing more.